This invention relates to a method and apparatus for raising lower cooler nutrient rich ocean water to mix with warmer nutrient poor ocean water to facilitate cooling of upper ocean water and phytoplankton growth.
It has long been known that deep waters of the earth's oceans are rich in nutrients. These include nitrate and phosphate, the result of decomposition of sinking organic matter (dead/detrital plankton) from surface waters. These deep water nutrients are located below the zone where sunlight can reach (below the “euphotic zone”) and photosynthesis cannot take place. As a consequence, these nutrients are normally unavailable to sea life which utilizes photosynthesis to thrive. The euphotic zone is that upper layer of water within which there is sufficient sunlight to support sea life processes. The sub-euphotic zone is the zone below the euphotic zone within which there is contained the nutrient substances, both organic and inorganic, for the growth and flourishing of sea life. When brought to the euphotic zone, these nutrients are utilized by phytoplankton, along with dissolved CO2 (carbon dioxide) and light energy from the sun, to produce organic compounds, through the process of photosynthesis.
Up-welling is an oceanographic phenomenon that involves upward motion of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water. The up-welling waters are usually rich in the dissolved nutrients (e.g., nitrogen and phosphate compounds) required for phytoplankton growth. This nutrient transport into the surface waters where sunlight is present (in the euphotic zone) is also required for phytoplankton growth. The combination of nutrient rich water from the depths and sunlight in the euphotic zone results in rapid growth of phytoplankton populations. Phytoplankton forms the base of marine food webs (or food chains).
Most up-welling areas are closely related to human fishing activities as natural up-welling supports some of the most productive fisheries in the world, including small species such as sardines, anchovies, etc. Natural up-welling regions therefore result in very high levels of primary production (the amount of carbon fixed by phytoplankton) in comparison to other areas of the ocean. High primary production propagates up the food chain because phytoplankton are at the base of the oceanic food chain. Up-welling fuels algae and shrimp like krill populations that feed small fish, which provide an important food source for a variety of sea life, from salmon to sea birds and marine mammals. And without up-welling, high-fat plankton such as krill stay at lower depths. The world's most productive fisheries are located in areas of coastal up-welling that bring cold nutrient rich waters to the surface (especially in the eastern boundary regions of the subtropics). About half the world's total fish catch comes from up-welling zones.
The food chain follows the course of:Phytoplankton-->Zooplankton-->Predatory zooplankton-->Filter feeders-->Predatory fish
Ocean water up-welling occurs naturally. For example, in some coastal areas of the ocean (and large lakes such as the North American Great Lakes), the combination of persistent winds, Earth's rotation (the Coriolis effect), and restrictions on lateral movements of water caused by shorelines and shallow bottoms induces upward and downward water movements. The Coriolis effect plus the frictional coupling of wind and water (Ekman transport) cause net movement of surface water at about 90 degrees to the right of the wind direction in the Northern Hemisphere and to the left of the wind direction in the Southern Hemisphere. Coastal up-welling occurs where Ekman transport moves surface waters away from the coast; surface waters are replaced by water that wells up from below.
Up-welling is most common along the west coast of continents (eastern sides of ocean basins). In the Northern Hemisphere, up-welling occurs along west coasts (e.g., coasts of California, Northwest Africa) when winds blow from the north (causing Ekman transport of surface water away from the shore). Winds blowing from the south cause up-welling along continents' eastern coasts in the Northern Hemisphere, although it is not as noticeable because of the western boundary currents. Up-welling also occurs along the west coasts in the Southern Hemisphere (e.g., coasts of Chile, Peru, and southwest Africa) when the wind direction is from the south because the net transport of surface water is westward away from the shoreline. Winds blowing from the north cause up-welling along the continents' eastern coasts in the Southern Hemisphere. Regions of natural up-welling include coastal Peru, Chile, Arabian Sea, western South Africa, eastern New Zealand, southeastern Brazil and the California coast.
Up-welling (and down-welling) also occur in the open ocean where winds cause surface waters to diverge from a region (causing up-welling) or to converge toward some region (causing down-welling). For example, up-welling takes place along much of the equator. The deflection due to the Coriolis effect reverses direction on either side of the equator. Hence, westward-flowing, wind-driven surface currents near the equator turn northward on the north side of the equator and southward on the south side. Surface waters are moved away from the equator and replaced by up-welling waters.
Up-welling of ocean water also influences sea-surface temperature. Up-welling waters which originate below the euphotic zone are colder than the surface waters they replace. Coastal up-welling and down-welling also influence weather and climate. Along the northern and central California coast, up-welling lowers sea surface temperatures and increases the frequency of summer fogs. Relatively cold surface waters chill the overlying humid marine air to saturation so that thick fog develops. Up-welling cold water inhibits formation of tropical cyclones (e.g., hurricanes), because tropical cyclones derive their energy from warm surface waters. During El Niño and La Niña, changes in sea-surface temperature patterns associated with warm and cold-water up-welling off the northwest coast of South America and along the equator in the tropical Pacific affect the inter-annual distribution of precipitation around the globe.
Scientists suspect that rising ocean temperatures and dwindling plankton populations are behind a growing number of seabird deaths, reports of fewer salmon and other anomalies along the West Coast. Coastal ocean temperatures are 2 to 5 degrees above normal, which is believed to be caused by a lack of natural up-welling.
Apart from their role in food productivity up the food chain, scientists also understand the role of the ocean's plants in removing carbon from the atmosphere. Tiny ocean plants that grow at the ocean's surface—phytoplankton—soak up more carbon dioxide than anything else on Earth, including dense tropical forests. Since ocean plants remove so much of the greenhouse gas from the atmosphere, they play an important role in mitigating global warming.
However, the normal tides, wind forces and currents are surface oriented and move horizontally or circumferentially over the earth, with but few geological inducements to create vertical currents that transfer waters from the depths. Natural up-welling has only a limited effect in displacement of the euphotic region waters with sub euphotic water, and vertical up-welling mass movement of waters as a result of natural effects is limited.
In light of the foregoing advantages resulting from the up-welling of sea water, and the limited effect of natural up-welling, there is a need for a method and apparatus which passively raises sea water and associated nutrients from ocean depths below the euphotic zone into the euphotic zone.